1. Field of the Invention
This invention relates generally to semiconductor wafer processing systems, apparatuses, and methods. In particular, the present invention relates to a structure with vertically-stacked process chambers which minimize the footprint while maximizing throughput of a semiconductor wafer processing system. For example, the present invention may be used to translate wafers within a near-atmospheric chemical vapor deposition (CVD) system, a rapid thermal oxidation system, or other types of wafer processing systems. The invention also particularly relates to a wafer transfer apparatus and method that moves semiconductor wafers between a loadlock chamber and a process chamber using a unitary transfer arm which pivots about a single rotational axis.
2. Description of Related Art
Conventionally, wafer transfer between loadlock chambers and process chambers is performed by complex apparatus. The complexity of the machinery has resulted in high cost of the apparatus, slow wafer processing and a short mean time between failures.
One example of a conventional wafer processing system is U.S. Pat. No. 4,934,315 to Linnebach et al. for xe2x80x9cSystem for Producing Semiconductor Layer Structures By Way of Epitaxial Growthxe2x80x9d. This multiple reactor chamber system accepts wafers for processing, where the wafers are loaded into respective holders in an atmospheric handler. The holders and wafers are stacked in a load chamber where each holder, carrying its respective wafer, is subsequently transferred along a linear path through the multiple reactor chambers. The reactor chambers are horizontally aligned along the linear path.
U.S. Pat. No. 4,822,756 to Hirayama for xe2x80x9cReaction Furnace and Method of Operating the Samexe2x80x9d discloses a reaction furnace including a wafer support boat which rolls from an elevator capsule through a loading chamber and into a treatment chamber. Although the loading chambers and the treatment chambers appear to be stacked in a vertical direction, the pressure gas system and vacuum system are horizontally disposed from the treatment chambers and thus disadvantageously increases the footprint of the reaction furnace.
U.S. Pat. No. 4,423,701 to Nath et al. for xe2x80x9cGlow Discharge Deposition Apparatus Including a Non-Horizontally Disposed Cathodexe2x80x9d discloses a multiple chamber glow discharge deposition apparatus having deposition chambers which vertically orient the wafers or substrates for processing. The deposition chambers are shown to be horizontally oriented with respect to one another. A rotatable arm expels the substrates from the chamber such that the arm pushes the substrates in one direction along channeled guides.
U.S. Pat. No. 4,816,098 to Davis et al. for xe2x80x9cApparatus for Transferring Workpiecesxe2x80x9d discloses a system in which wafers are loaded onto the system in a vacuum wafer carrier which is held under vacuum to reduce contamination of the wafers. The wafers are transferred into a cluster tool having multiple process modules via a vacuum loadlock and a 2-axis robot arm which only has the capability of transporting a single wafer at a time.
U.S. Pat. No. 5,664,254 to Ohkura et al. for xe2x80x9cSubstrate Processing Apparatus and Substrate Processing Methodxe2x80x9d discloses a stacking arrangement for a plurality of process units. Although the process units may be vertically stacked, only one main handler is provided for transferring substrates to each of the process units, whereby the throughput of each process unit cannot be maximized. The patent also discloses a plurality of holding arms arranged in a 3-stage structure for transferring a substrate or wafer. The holding arms are mounted on the main handler and are actuated by a complex arrangement including a vertical drive shaft and motor in combination with a horizontally oriented convey base having a drive motor and belt to actuate each holding arm.
U.S. Pat. No. 5,058,526 to Matsushita et al. for xe2x80x9cVertical Load Lock Reduced-Pressure Type Chemical Vapor Deposition Apparatusxe2x80x9d discloses a loading/unloading chamber which is similar to a loadlock chamber found in a conventional cluster tool. A cooler including refrigerant-circulating tubes located in an unloading part of a loading/unloading chamber cools the treated wafers.
U.S. Pat. No. 5,664,925 to Muka et al. for xe2x80x9cBatchloader for Load Lockxe2x80x9d discloses a conventional single-wafer scissor-type transfer arm. Similar conventional single-wafer scissor-type transfer arms are disclosed by U.S. Pat. No. 5,613,821 to Muka et al. for xe2x80x9cCluster Tool Batchloader of Substrate Carrierxe2x80x9d and U.S. Pat. No. 5,607,276 to Muka et al. for xe2x80x9cBatchloader for Substrate Carrier on Load Lockxe2x80x9d.
U.S. Pat. No. 5,778,968 to Hendrickson et al. for xe2x80x9cMethod for Heating or Cooling Wafersxe2x80x9d discloses a method for heating or cooling a substrate enclosed vacuum chamber using gas having an adjustable pressure above the wafer. Similarly, U.S. Pat. No. 5,588,827 to Muka for xe2x80x9cPassive Gas Substrate Thermal Conditioning Apparatus and Methodxe2x80x9d discloses a heat transfer plate, located in a thermal conditioning chamber, which is either heated or cooled to change the temperature of a substrate.
A semiconductor substrate or wafer processing system and a substrate or wafer transfer apparatus in accordance with the present invention overcomes the disadvantages of conventional systems discussed above. In accordance with the present invention, a semiconductor wafer processing system includes a multi-chamber module, the multi-chamber module having a plurality of vertically-stacked loadlock-process chamber assemblies, an atmospheric-pressure front end unit having an atmospheric-pressure front end robot for transporting semiconductor wafers between a wafer cassette and the loadlock-process chamber assemblies, a common process chemical delivery system for each stack of chamber assemblies, and a dedicated wafer transfer apparatus for each loadlock-process chamber assembly. The processing system may also include two or more multi-chamber modules oriented in a linear array. A loadlock chamber is dedicated to each process chamber, the chambers together forming a respective loadlock-process chamber assembly. A cooling plate is disposed within each loadlock chamber below a single-pivot transfer arm of the wafer transfer apparatus. The cooling plate is provided with lift pins for removing wafers from the pivot transfer arm. A wafer chuck assembly having a chuck clamping surface and pins is provided within each process chamber for positioning wafers within the process chamber. In one embodiment of the present invention, the wafer chuck assembly translates a wafer within the process chamber past a chemical vapor deposition injector for processing.
One wafer transfer apparatus serves each loadlock-process chamber assembly. Each wafer transfer apparatus includes a transfer arm adapted to carry and transfer two or more wafers between the loadlock chamber and the process chamber. The transfer arm pivots about a single pivot axis extending through the loadlock chamber. The transfer apparatus has the capacity to simultaneously carry two wafers between the loadlock chamber and the process chamber. The wafer transfer apparatus also includes a retracted/home position and an extended position, wherein the single pivot axis allows the transfer arm to pivot between the retracted and extended positions. The cooling plate is disposed below the pivot arm when the pivot arm is in the retracted position. The wafer transfer apparatus also includes a lower wafer shelf and an upper wafer shelf integrated within the transfer arm.
Another aspect of the present invention is directed to a method of transferring the unprocessed wafer from the loadlock chamber to the process chamber, transferring the unprocessed wafer from the upper wafer shelf to a semiconductor wafer chuck mounted in the process chamber, translating the semiconductor wafer chuck from a retracted position, to an extended position where the wafer is processed, simultaneously transferring the processed wafer and a second unprocessed wafer between the loadlock chamber and the process chamber, and transferring the processed wafer from the lower wafer shelf to the cooling plate.
It is an object of the present invention to provide a wafer processing system having multiple loadlock-process chamber assemblies, each assembly having one loadlock chamber dedicated to a process chamber and a dedicated transfer arm which moves wafers between respective loadlock and process chambers.
It is an object of the present invention to vertically stack two or more loadlock-process chamber assemblies to form a multi-chamber module in order to reduce the system footprint and thus optimize the vertical orientation and layout of the loadlock-process chamber assembly stacks.
It is another object of the present invention to align the multi-chamber modules in a linear fashion with a single atmospheric-pressure front end wafer transfer system delivering substrates to all loadlock chambers to optimize the footprint of the processing system.
It is another object of the present invention to provide a common process chemical delivery system and local control system for each multi-chamber module.
It is another object of the present invention to optimize wafer flow paths and process timing for a linear array, vertically-stacked processing system and method in order to maximize throughput of each process chamber and of the full processing system.
It is another object of the present invention to optimize the number of process chambers within a footprint to increase processing system throughput.
It is a further object of the present invention to provide a new wafer transfer arm and wafer transfer method which moves semiconductor wafers from a single atmospheric-pressure front end robot, through a loadlock chamber, and into a wafer process chamber, in which the transfer arm pivots about a single rotational axis with one pivot point located on the transfer arm to side-load the process chamber.
It is another object of the present invention to provide a transfer arm having the capacity to carry two wafers in order to facilitate and expedite wafer transfer between the loadlock chamber and the process chamber. In particular, it is an object of the present invention to provide a transfer arm which has the capacity to carry an unprocessed wafer and a processed wafer at the same time in order to maximize system throughput.
It is another object of the present invention to provide a wafer cooling plate to reduce wafer cooling time after a wafer is processed to facilitate wafer transfer out of the loadlock and into a cassette maximizing parallel steps within the processing system and thus increasing throughput of the processing system.